Adding a smaller pulley to the current VT1-535 would net you min gains but would lower your safety margin without proper changes to the software. On average you might pickup about 10-15 whp. The down side is the safety calculations in the software are configured to keep the motor safe in most conditions with the current level of boost. One of the changes we make in our higher boost kits is we use a different tune knowing that the vehicle is adding intercooling or is going to be on high quality 93+ octane fuel. In the case of the VT1-535 non intercooled kit we would actually add more safety margin to the current tune if we were going to run higher levels of boost on it. This would allow it to make a small amount of additional power in proper conditions but also keep it safe when needed.

+1.

OP: You'll pick up more power going with a set of Macht Schnell Track Pipes.